In household electrical systems, it is common to supply a wall outlet with electrical power through a wall switch positioned near an entryway. A lamp may then be plugged into the switched wall outlet. If the switch at the lamp is left on, the lamp can be turned on and off from the wall switch. This allows a person entering a dark room to turn on the lamp from the wall switch and avoids the need to search for the lamp switch in the dark.
Commonly, however, it is more convenient to turn the lamp off using the switch near the lamp. As a result, when the person leaves and later re-enters the room after dark, an attempt to turn on the lamp at the wall switch fails. Also, if the wall switch is turned off, the lamp cannot be turned on using the lamp switch. The bedside lamp illustrates the problem. While it is convenient to turn the lamp on using the wall switch when entering the room after dark, it is more convenient to use the switch near the lamp to turn the lamp off when retiring. As a result, in the morning when the room is well lit by daylight, the bedside lamp switch is typically left switched off. Thus, at nighttime when the room is reentered, the wall switch can't be used to turn the lamp on again.
It would thus be desirable to provide a switching mechanism device that can be used to control a lamp that is plugged into a switched outlet from either the wall switch or the lamp switch.
For ease of installation and to limit expense, it would further be desirable to provide a field installable control device that can be used without requiring modification to the wall switch, the lamp, or the lamp switch, or alternatively to provide a new lamp fixture that can be used without modifying the wall switch or other parts of the existing wiring.